1. Field of the Invention
The invention relates to the manufacture of curved laminated glass sheets having two or more single glass sheets bonded together with adhesive plastic layers. It particularly relates to a method for bending the silicate glass sheets intended to become curved laminated glass sheets, in which the glass sheets are individually heated to bending temperature in a passthrough oven, and are individually bent with the aid of a full-surface bending mold.
2. Discussion of the Background
The most well-known method for bending glass sheets intended to become laminated glass sheets, for example windshields for motor vehicles, consists of stacking the associated glass sheets, i.e. the two single glass sheets in a common glass laminate, on a peripheral bending mold and passing them together through a heating oven, where, under the effect of their own weight they come to rest against the peripheral bending mold when they attain the bending temperature. The disadvantages of this method are, first, that it is not possible to produce complicated sheet shapes in this manner, and second, that all glass sheets bent in this manner also have, to a greater or lesser degree, a spherical bending, i.e. are curved in both surface directions.
In order to avoid these disadvantages, it is also already known to bend the glass sheets intended for the manufacture of laminated glass sheets into the desired shape with the aid of a bending press. In one of these known press bending methods the two glass sheets are brought together between the two bending molds of the bending press and are bent jointly (DE-AS 11 92 373). According to another known press bending method the glass sheets are hung individually on supports between the bending molds of a bending press, and are bent and cooled individually (DE-OS 19 29 115).
These known press bending methods for multiple glass sheets are also associated with substantial disadvantages. When the sheets are together as they are being bent by two mechanical press tools, of which generally the convex bending tool consists of a full-surface bending mold, and the concave bending tool consists of a frame bending mold, the two glass sheets are cooled differently on their surfaces that contact the bending mold, so that the stacked glass sheets separate from each other along the edges. This incongruent deformation of the two glass sheets cannot be completely reversed. In another known method, namely the press bending of the individual glass sheets while they are suspended, it is also not possible to attain a fully congruent form of the two single glass sheets, because even the smallest difference in the cooling conditions after the pressing step will lead to deformations which make the glass sheets unusable for further processing into laminated glass.